FREEDOM D3.3 - Cooperative schemes in the femto-based networks

We investigate cooperative transmission schemes that can be applied to joint deployments of femto-access points (FAPs) and macro base stations (MBS) by exploiting backhaul communication links between nodes at the data-plane level. First, we study the effects of some hardware impairments, such as time misalignment and carrier offset compensation, on cooperation performance. Additionally, we look into the MIMO X channel as a general framework that subsumes all possible types of cooperative communication between two sources and two destinations (broadcast, interference or multiple access channels), assuming full channel state information at the transmitters. Since FAPs have a delay constrained backhaul the cooperation of multiple FAPs becomes sensitive to random delays at the sources. In this regard we have provided two solutions: a) appropriate delay-tolerant cooperative space-time coding and decoding schemes and b) specific cooperative schemes for critical delay applications.